1. Field of the Invention
The present invention relates to an echo canceler for eliminating the echoes generated at a proximal end of a transmission line of a telecommunication system through which speakers at the opposite ends of the line can talk to each other.
2. Description of the Related Art
In a prior art echo canceler, a single adaptive filter circuit and a single subtractor are provided. That is, in this adaptive filter circuit, tap coefficients are calculated in accordance with an error signal and a received signal, and a pseudo echo signal is generated in accordance with the tap coefficients and the received signal. Also, the subtracter subtracts the pseudo echo signal from a transmitting signal, thus cancelling echoes in the transmitting signal. In the prior art echo canceler, however, when the background noise is large at the proximal end of a line or when it is impossible to determine whether the line is for a 2-wire system or a 4-wire system, the characteristics of detecting double-talk are degraded, and the characteristics of tap coefficients are not stable. This will be explained later in detail.